Packages for electronic devices are used to house a wide variety of electronic devices. Typically, these packages are semiconductor packages mounted onto a printed circuit board (PCB). Several schemes of mounting a device onto a PCB are available. For example, surface-mount technology (SMT) is an approach of mounting electronic device packages directly onto the PCB surface, whereas through-hole technology refers to a mounting scheme used for pin-through-hole (PTH) electronic device packages that involves the usage of pins on the components that are inserted into holes drilled in the PCB and soldered to pads on the opposite side.
A package has a natural resonant frequency depending on its mechanical properties, i.e. the package has a tendency to oscillate at maximum amplitude at certain resonant frequencies. At these frequencies, even small periodic driving forces can produce large amplitude vibrations, because the package stores vibration energy. For example, a semiconductor package may incorporate sensor elements, e.g. inertial sensor elements such as accelerometers or angular rate sensors, which may be used in automotive applications. In case of an operating frequency of a transducer sensor element close to the natural resonant frequency of the package assembly, the sensor assembly may malfunction or fail, because the sensor transducer element may be stressed, distorted or even damaged.
U.S. Pat. No. 5,889,658 shows a package assembly for encapsulating and vertically surface mounting a semiconductor device using a single row of leads. Instead of using a standard lead shape and a standard pitch, the lead shape can be modified for adjustment of the resonant frequency of the package by varying an external lead offset.
U.S. Pat. No. 5,644,081 shows a through-hole mounted microaccelerometer package with a free formed lead frame that enhances the rigidity of the package and reduces excess vibration in the accelerometer.
U.S. Pat. No. 5,659,950 describes a method of forming a package assembly that encapsulates an electronic die. A single inline package is provided with one row of leads protruding from one side of the package and two additional supports connected to a different side for improving the rigidity and natural bending frequency of the shown package assembly.